This invention relates to a sputtering target suitable for the formation of an alloy film for electrical wiring which is excellent in electrical conductivity, workability, oxide layer formation properties, and other characteristics.
In recent years, much attention has been paid to an active matrix type liquid crystal display device in which a thin film transistor (TFT) having an amorphous silicon (a-Si) film is used as a switching element.
When TFT arrays are formed by using an amorphous glass substrate and the a-Si film which can be formed at a low temperature, there can be provided a panel display (flat type television) having great area, high definition, high picture quality, as well as being inexpensive. In order to obtain the active matrix type liquid crystal display device having the finest possible picture elements and the greatest area, signal wiring extending to TFT, i.e., gate wiring and data wiring, must be thin and long.
For example, in the case of employing a reverse stagger type TFT structure which is constituted by superposing an insulating film and a a-Si film on the glass substrate having provided thereon gate electrode wiring, it is required that the gate electrode wiring be thin, have sufficiently low resistance, and withstand chemicals used in subsequent steps.
As raw materials for the gate electrodes which can satisfy such requirements, there have been heretofore used various metallic films of tantalum (Ta), titanium (Ti) and the like. However, in order to increase further the area and the definition of the liquid crystal display, raw material having lower electrical resistance, better workability and high resistance to various chemicals used in the subsequent chemical treatment steps is demanded.
Moreover, in the case of employing a stagger type TFT structure in which a drain and a source electrode wiring is disposed on the substrate, it is required that the drain and the source electrode wiring possess the above-mentioned characteristics.
On the other hand, a semiconductor integrated circuit using a single crystal Si substrate suffers similar problems. For example, an impurity-doped polycrystalline silicon film is usually used for the gate electrode wiring of an MOS transistor used in a memory integrated circuit typified by a dynamic RAM.
However, in order to achieve further microminiaturization and high integration of the elements, the polycrystalline silicon film has a specific resistance that is too high. As a raw material which has lower specific resistance than that of the polycrystalline silicon film and can withstand high temperatures, there are a molybdenum/silicide (MoSi.sub.2) film and the like. However, when the dynamic RAM or the like of 1 M bit or more is to be realized by use of this molybdenum/silicide film, resistance of the electrode wiring increases disadvantageously.
In a semiconductor device using a conventional a-Si film, a single crystal Si substrate or the like, in order to achieve further microminiaturization and high integration of the elements, resistance of the electrode wiring increases disadvantageously. Moreover, raw materials for the electrode wiring are required to have excellent workability, high resistance to various treatments, and good and stable ohmic contact properties with Si, in addition to the low specific resistance.